Hollow Core Protects Optical Fibers from UV Light

ERLANGEN, Germany, and BRAUNSCHWEIG, Germany, July 3, 2014 — A new type of optical fiber can guide UV laser light without sustaining the damage often seen in conventional fibers.

A microscopic image of a hollow core optical fiber. Courtesy of the Max Planck Institute.
Developed by a team from the Max Planck Institute and the Centre for Quantum Engineering and Space-Time Research (QUEST) at the Physical-Technical Federal Agency, the new optical fiber has a hollow core.

Traditional optical fibers have a solid glass core, which is most often used to transport light of various spectral ranges, from IR to visible light. UV light, however, is different — its shorter wavelength is strongly absorbed into the glass and subsequently damages the optical fibers.

This new microstructured photonic crystal fiber features a Kagome structure, which is a pattern consisting of triangles and hexagons in a regular arrangement.

The hollow core is 20 µm in diameter, and was designed for single-mode light guiding. According to the researchers, it has an intensity distribution similar in shape to a Gaussian bell curve. In the study, the researchers found that a UV wavelength measuring 280 nm allowed single-mode transmission at 15 mW with no UV-induced damage.

Near-field intensity profiles of a single-mode fiber measured with a UV beam from different directions. Courtesy of the Physical-Technical Federal Agency.
The new optical fiber was also tested in QUEST’s spectroscopic investigation of trapped ions. The fibers stabilized the UV laser beam, allowing a more comprehensive look at the ions’ internal state and causing no damage.

In addition to the study of ions, the new optical fiber could benefit applications such as quantum computing, fluorescence microscopy and greenhouse gas spectroscopy.